1. Field of the Invention
The technical scope of the invention is that of safety and arming devices for the pyrotechnic train of a projectile, and namely micro-machined safety and arming devices.
2. Description of the Related Art
Safety and arming devices (DSA) are well known. They generally incorporate a screen obturating a transmission channel linking a detonator and pyrotechnic charge.
The screen therefore is interposed on the transmission of the detonic wave between the detonator and the charge and prevents the latter from functioning.
One of the problems encountered with conventional devices lies in their volume. The parts are relatively large to be able to ensure the interruption of the pyrotechnic chain. Drive means enabling the screen to be moved are necessarily powerful. Springs are used, more often than not, which remain tensed during the storage phases, and which can lead to a deterioration of their mechanical properties and to a reduction in the weapon's reliability.
In the past few years, the manufacture of all or part of safety devices has been proposed using chips that incorporate electromagnetic elements micro-machined or micro-engraved either in an element deposited on a substrate or directly on the substrate itself. This technology, known by the term MEMS (Micro Electro Mechanical System) in fact currently enables micro mechanisms to be manufactured that implement technology close to that enabling the manufacture of electronic integrated circuits.
U.S. Pat. No. 6,964,231 describes such a micro-machined safety device incorporating a shutter that carries a pyrotechnic charge and slides by the action of the centrifugal force. This shutter is itself held immobile by a lock, which is made to retract by the acceleration of the projectile being fired.
Another tipping lock enables the shutter to be released and moved to the position in which it is armed by the force of centrifugal inertia. The tipping lock is activated by a gas-generating pyrotechnic composition whose ignition is controlled by electronic means.
Such a safety and arming device requires two independent environmental conditions to be used to ensure arming: longitudinal firing acceleration and centrifugal acceleration. This double safety enables the device to conform to the strictest standards in terms of projectile arming and safety (STANAG 4187).
It is however complicated in structure and namely the second lock (tipping lock) requires the implementation of a pyrotechnic composition as well as means to ignite such composition. Electronics must be provided to pilot the functioning of this MEMS that are not well adapted to use in medium caliber ammunition (caliber of less than 40 mm) in which there is little available space.